openwrt/target/linux/bcm27xx/patches-5.4/950-0646-spi-Force-CS_HIGH-if-GPIO-descriptors-are-used.patch

From 5f2eface651ba5da9caaa84ccca14b9202ba6202 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Fri, 17 Apr 2020 10:46:19 +0100
Subject: [PATCH] spi: Force CS_HIGH if GPIO descriptors are used

Commit f3186dd87669 ("spi: Optionally use GPIO descriptors for CS GPIOs")
amended of_spi_parse_dt() to always set SPI_CS_HIGH for SPI slaves whose
Chip Select is defined by a "cs-gpios" devicetree property.

This change breaks drivers whose probe functions set the mode field of
the spi_device because in doing so they clear the SPI_CS_HIGH flag.

Fix by setting SPI_CS_HIGH in spi_setup (under the same conditions as
in of_spi_parse_dt()).

See also: 83b2a8fe43bd ("spi: spidev: Fix CS polarity if GPIO descriptors are used")

Fixes: f3186dd87669 ("spi: Optionally use GPIO descriptors for CS GPIOs")
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 drivers/spi/spi.c | 9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -3116,6 +3116,7 @@ static int __spi_validate_bits_per_word(
  */
 int spi_setup(struct spi_device *spi)
 {
+	struct spi_controller *ctlr = spi->controller;
 	unsigned	bad_bits, ugly_bits;
 	int		status;
 
@@ -3133,6 +3134,14 @@ int spi_setup(struct spi_device *spi)
 		(SPI_TX_DUAL | SPI_TX_QUAD | SPI_TX_OCTAL |
 		 SPI_RX_DUAL | SPI_RX_QUAD | SPI_RX_OCTAL)))
 		return -EINVAL;
+
+	if (ctlr->use_gpio_descriptors && ctlr->cs_gpiods &&
+	    ctlr->cs_gpiods[spi->chip_select] && !(spi->mode & SPI_CS_HIGH)) {
+		dev_warn(&spi->dev,
+			 "setup: forcing CS_HIGH (use_gpio_descriptors)\n");
+		spi->mode |= SPI_CS_HIGH;
+	}
+
 	/* help drivers fail *cleanly* when they need options
 	 * that aren't supported with their current controller
 	 * SPI_CS_WORD has a fallback software implementation,